Cellular signal transduction is a mechanism whereby external stimuli that regulate cellular processes are relayed from receptors at the surface of a cell to its interior. One of the key biochemical mechanisms of signal transduction involves the reversible phosphorylation of proteins. The phosphorylation state of a protein, which can affect its conformation, enzymatic activity, and cellular location, is modified through the reciprocal actions of protein kinases (“PKs”) and protein phosphatases. The regulation, or lack of regulation, of protein kinases can thus have a dramatic effect on cellular behavior.
During cellular signal transduction, the function of each receptor kinase is determined by its pattern of expression, ligand availability, and the array of downstream signal transduction pathways that are activated by it. One example of a pathway includes a cascade of Growth Factor receptor tyrosine kinases (“RTKs”), such as EGF-R, PDGF-R, VEGF-R, IGF1-R, and the Insulin receptor, that deliver signals via phosphorylation to other kinases, such as Src tyrosine kinase and Raf, Mek, and Erk serine/threosine kinases. See, e.g., Davis, B. D., et al., Microbiology 838-841 (4th ed., 1990); and Brott, B. K., et al., Cell Growth Differ. 4(11):921-929 (1993). Each of these kinases play related, but functionally distinct, roles. The loss of regulation of the Growth Factor signaling pathway is a frequent occurrence in disease states such as cancer.
Aberrant expression of, or mutations in, protein kinases have been shown to lead to either uncontrolled cell proliferation (for example, malignant tumour growth) or to defects in key developmental processes. Protein kinases have been implicated as targets in central nervous system disorders (such as Alzheimer's), inflammatory disorders (such as psoriasis), bone diseases (such as osteoporosis), atheroscieroses, restenosis, thrombosis, metabolic disorders (such as diabetes), and infectious diseases (such as viral and fungal infections).
Because the regulation and/or inhibition of protein kinases can aid in the treatment and/or prevention of a variety of diseases, significant research has been directed at discovering compounds that affect protein kinase activity. This research is similar to that which may have led to discovery of the compounds disclosed by PCT application WO 91/09598 and U.S. Pat. No. 5,811,432, which are of the formula wherein one of A, B, D, and E is nitrogen and the others are carbon; X and Y can be, for example, halogen or hydroxy; R1 is (C1-C6)alkyl or an amide; R2 is (C1-C8)alkyl, preferably (C3-C8)alkyl; and W is, for example, hydrogen or (CO2-C10)alkanoyl. These compounds, which are not reported to be kinase inhibitors, are allegedly inhibitors of prostaglandin H2 synthase, 5-lipoxygenase, and interleukin-1 biosynthesis, and allegedly are anti-inflammatory and analgesic agents.
Examples of compounds that are allegedly protein kinase inhibitors are disclosed by PCT application WO 97/13771. These compounds are of the formula wherein X is nitrogen or CH; R2, Y, R3, and R5 are each selected from a large number of moieties; the group represents, for example, a 5-membered heterocyclic ring; and each R1 independently represents a 5- or 6-membered heterocyclic ring.
PCT application WO 98/02437 discloses compounds similar in structure to those described above, i.e.: 
As above, R1 represents a 5- or 6-membered heterocyclic ring. These compounds are also allegedly protein tyrosine kinase inhibitors.
PCT application WO 98/02438 discloses compounds of the formula: wherein X is nitrogen or CH; R1, R2, and Y are each selected from a large number of moieties; U is a 5- to 10-membered mono or bicyclic ring system; the group represents, for example, a 5-membered heterocyclic ring; and R″ represents a phenyl group or a 5- or 6-membered heterocyclic ring. These compounds are also allegedly protein tyrosine kinase inhibitors.
PCT application WO 98/23613 discloses compounds of the formula: wherein Z can be a group of the formula and R6 is H, halogen, cyano, alkyl, or substituted alkyl. These compounds can allegedly be used in the treatment of hyperpoliferative diseases such as cancer.
PCT application WO 99/21859 discloses compounds of the formula: wherein the R groups are variously defined. These compounds are reportedly useful as protein kinase inhibitors.
PCT application WO 99/37622 discloses a compound of the formula: which is allegedly useful as a PDE4 and TNF-α antagonist.
U.S. Pat. No. 5,916,891 discloses a compound of the formula: which is a derivative of the compound of formula: which is allegedly a p38/Raf inhibitor. Both of these compounds share structural features with rofecoxib, which is sold by Merck under the tradename Vioxx® and which has the formula: and celecoxib, which is sold by Monsanto and which has the formula: 
Final examples of compounds that are allegedly useful as protein kinase inhibitors are disclosed in PCT applications WO 87/04928 and WO 96/16964.
Despite the large number of compounds that reportedly inhibit protein kinase activity, a need still exists for compounds that can be used in the treatment and/or prevention of cancer and other diseases in humans. This is due, in part, to bioavailability, toxicity, and other problems which render many of the known protein kinase inhibitors unsuited for clinical development.
This invention is therefore directed in part to compounds which modulate protein kinase (“PK”) signal transduction by affecting the enzymatic activity of tyrosine kinases and thereby interfering with the signals transduced by them. More particularly, the present invention is directed to compounds which modulate the RTK, cellular tyrosine kinase (“CTK”) and/or serine/threonine kinase (“STK”) mediated signal transduction pathways as a therapeutic approach to treat many kinds of solid tumors, including but not limited to carcinoma, sarcomas including Kaposi's sarcoma, leukemia, erythroblastoma, glioblastoma, meningioma, astrocytoma, melanoma and myoblastoma. Other specific indications related to these include, but are not limited to, brain cancers, bladder cancers, ovarian cancers, gastric cancers, pancreas cancers, colon cancers, blood cancers, lung cancers, bone cancers and leukemias.
Further examples, without limitation, of the types of disorders related to unregulated PK activity that the compounds described herein may be usefull in preventing, treating and/or studying, are cell proliferative disorders, fibrotic disorders and metabolic disorders. Cell proliferative disorders, which may be prevented, treated or further studied by the present invention include cancers, blood vessel proliferative disorders and mesangial cell proliferative disorders.
Blood vessel proliferative disorders refer to angiogenic and vasculogenic disorders generally resulting in abnormal proliferation of blood vessels. The formation and spreading of blood vessels, or vasculogenesis and angiogenesis, respectively, play important roles in a variety of physiological processes such as embryonic development, corpus luteum formation, wound healing and organ regeneration. They also play a pivotal role in cancer development. Other examples of blood vessel proliferation disorders include arthritis, where new capillary blood vessels invade the joint and destroy cartilage, and ocular diseases, like diabetic retinopathy, where new capillaries in the retina invade the vitreous, bleed and cause blindness. Conversely, disorders related to the shrinkage, contraction or closing of blood vessels, such as restenosis, are also implicated.
Fibrotic disorders refer to the abnormal formation of extracellular matrices. Examples of fibrotic disorders include hepatic cirrhosis and mesangial cell proliferative disorders. Hepatic cirrhosis is characterized by the increase in extracellular matrix constituents resulting in the formation of a hepatic scar. Hepatic cirrhosis can cause diseases such as cirrhosis of the liver. An increased extracellular matrix resulting in a hepatic scar can also be caused by viral infection such as hepatitis. Lipocytes appear to play a major role in hepatic cirrhosis. Other fibrotic disorders implicated include atherosclerosis. Mesangial cell proliferative disorders refer to disorders brought about by abnormal proliferation of mesangial cells. Mesangial proliferative disorders include various human renal diseases, such as glomerulonephritis, diabetic nephropathy, malignant nephrosclerosis, thrombotic microangiopathy syndromes, transplant rejection, and glomerulopathies. The PDGF-R has been implicated in the maintenance of mesangial cell proliferation. Floege et al., Kidney International 43:47S-54S (1993).
As noted previously, PKs have been associated with such cell proliferative disorders. For example, some members of the RTK family have been associated with the development of cancer. Some of these receptors, like the EGFR (Tuzi et al., Br. J. Cancer 63:227-233 (1991); Torp et al., APMIS 100:713-719(1992)) HER2/neu (Slamon et al., Science 244:707-712 (1989)) and PDGFR (Kumabe et al., Oncogene, 7:627-633 (1992)) are over-expressed in many tumors and/or are persistently activated by autocrine loops. In fact, in the most common and severe cancers these receptor over-expressions have been demonstrated Akbasak and Suner-Akbasak et al., J. Neurol. Sci., 111:119-133 (1992); Dickson et al., Cancer Treatment Res. 61:249-273 (1992); Korc et al., J. Clin. Invest. 90:1352-1360 (1992)) and autocrine loops (Lee and Donoghue, J. Cell. Biol., 118:1057-1070 (1992); Korc et al., supra; Akbasak and Suner-Akbasak et al., supra). For example, EGFR has been associated with squamous cell carcinoma, astrocytoma, glioblastoma, head and neck cancer, lung cancer and bladder cancer. HER2 has been associated with breast, ovarian, gastric, lung, pancreas and bladder cancer. PDGFR has been associated with glioblastoma, lung, ovarian, melanoma and prostate. The RTK c-met has been generally associated with hepatocarcinogenesis and thus hepatocellular carcinoma. C-met has been linked to malignant tumor formation. More specifically, the RTK c-met has been associated with, among other cancers, colorectal, thyroid, pancreatic and gastric carcinoma, leukemia and lymphoma. Additionally, over-expression of the c-met gene has been detected in patients with Hodgkins disease, Burkitts disease, and the lymphoma cell line. Flk has been associated with a broad spectrum of tumors including without limitation mammary, ovarian and lung tumors as well as gliomas such as gtioblastoma. IGF-IR, in addition to being implicated in nutritional support and in type-II diabetes, has also been associated with several types of cancers. For example, IGF-I has been implicated as an autocrine growth stimulator for several tumor types, e.g., human breast cancer carcinoma cells (Arteaga et al., J. Clin. Invest. 84:1418-1423 (1989)) and small lung tumor cells (Macauley et al., Cancer Res., 50:2511-2517 (1990)). In addition, IGF-I, integrally involved in the normal growth and differentiation of the nervous system, appears to be an autocrine stimulator of human gliomas. Sandberg-Nordqvist et al., Cancer Res. 53:2475-2478 (1993). The importance of the IGF-IR and its ligands in cell proliferation is further supported by the fact that many cell types in culture (fibroblasts, epithelial cells, smooth muscle cells, T-lymphocytes, myeloid cells, chondrocytes, osteoblasts, the stem cells of the bone marrow) are stimulated to grow by IGF-I. Goldring and Goldring, Eukaryotic Gene Expression, 1:301-326 (1991). In a series of recent publications, Baserga even suggests that IGF-IR plays a central role in the mechanisms of transformation and, as such, could be a preferred target for therapeutic interventions for a broad spectrum of human malignancies. Baserga, Cancer Res., 55:249-252 (1995); Baserga, Cell, 79:927-930 (1994); Coppola et al., Mol. Cell. Biol., 14:4588-4595 (1994). STKs have been implicated in many types of cancer including notably breast cancer. Cance, et al., Int. J. Cancer, 54:571-77 (1993).
The association between abnormal PK activity and disease are not restricted to cancer, however. For example, RTKs have been associated with diseases such as psoriasis, diabetes mellitus, endometriosis, angiogenesis, atheromatous plaque development, Alzheimer's disease, epidermal hyperproliferation and neurodegenerative diseases, age-related macular degeneration, hemangiomas. For example, EGFR is indicated in corneal and dermal wound healing. Defects in the Insulin-R and the IGF-1R have been indicated in type-II diabetes mellitus. A more complete correlation between specific RTKs and their therapeutic indications is set forth in Plowman et al., DN&P 7:334-339 (1994). As noted previously, not only RTKs but CTKs as well including, but not limited to, src, abl, fps, yes, fyn, lyn, lck, blk, hck, fgr and yrk (reviewed by Bolen et al., FASEB J., 6:3403-3409 (1992)) are involved in the proliferative and metabolic signal transduction pathway and thus would be expected, and in fact have been shown, to be involved in many PTK-mediated disorders to which the present invention is directed. For example, mutated src (v-src) has been demonstrated as an oncoprotein (pp60v-src) in chicken. Moreover, its cellular homolog, the proto-oncogene pp60c-src transmits oncogenic signals of many receptors. For example, over-expression of EGFR or HER2/neu in tumors leads to the constitutive activation of pp60c?src, which is characteristic for the malignant cell but absent from the normal cell. On the other hand, mice deficient in the expression of c-src exhibit an osteopetrotic phenotype, indicating a key participation of c-src in osteoclast function and a possible involvement in related disorders. Similarly, Zap70 is implicated in T-cell signaling.
PKs have been implicated in other diseases and disorders. For example, STKs have been associated with inflamation, autoimmune disease, immunoresponses, and hyperproliferation disorders such as restinosis, fibrosis, psoriasis, osteoarthritis and rheumatoid arthritis. PKs have also been implicated in embryo implantation and the compounds of this invention may provide an effective method of preventing embryo implantation. Finally, both RTKs and CTKs are currently suspected as being involved in hyperimmune disorders.